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TUSKS AND MOLARS

the maxillae, and so forth. This state of affairs, together witl
the presence of the huge tusks, has, as it were, pushed back th€
nasal orifices to near the top of the skull is a very "Whale-like
fashion. As in the Getacea, the nasal bones are limited in size
and the premaxillae send up processes to join, the frontals anc
the nasals. There is a straight and somewhat slender zygomatic
arch, but the orbit is not separated from the temporal fossa. The
malar bone is small, and, as in Rodents, forms the middle parl
of the zygoma. This is not the case with most Ungulata, The
symphysis of the mandibles forms a spout-like rim. The scapule
has a narrow prescapular, but a very wide postscapular region
The spine has a strong process projecting backwards from neai
its middle; this is a point of likeness to certain Hodents, JNfc
Elephant has a clavicle. The most remarkable feature about
the fore-limb is the separation and crossing of the radius anc
ulna. The arms of these animals are permanently fixed in th«
position of pronation. The foot is short, and the bones of the
carpus are serially arranged. There are, however, traces of 8
commencing interlocking of these bones in many forms. The
hind-feet are somewhat smaller than the fore-feet, and the tibic
and fibula are both developed.
As to the teeth, this genus is to be distinguished from allied
forms by the presence of tusks in the upper jaw only. These
tusks have no bands of enamel such as characterise those o
Mastodon. They are incisors. There is, however, a trac<
of the former enamelling in the shape of a patch at the tip
which soon wears away. The molar teeth of 38lep7ia*s are &
large that the jaws cannot accommodate more than at tin
most two and a part of a third at a time. These are gradu
ally replaced by others to the number of three, the replace
ment of teeth suggesting that of the Manatee. Each molar i
deeply ridged, the interstices between the ridges being filled u;
with cement. As the tooth wears away, therefore, the surfac
continues to be flat. Each ridge consists of a core of dentin
surrounded by a coat of enamel. The number of these ridg€
varies greatly from species to species. The Indian Elephant 3
one of those which have the greatest number of plates in a sing]
tooth, as many as twenty-seven.1 Of the six molars which eventu
1 It must be borne in mind that the teeth increase in complexity, those fin
pushed up having the fewest plates.    The first has only four transverse plate*.